This is still much different from what you may conclude solely based on the associations that exist between low vitamin D and all sorts of ailments, though. Evidence that vitamin D(3) supplements are able to reduce the risk of bone fractures, diabetes, cardiovascular diseases, cancer, depression, osteoarthritis, multiple sclerosis, and other immune related diseases is still preliminary. Very unfortunate in view of big research dollars that have been spend without yielding D-finite results and hundreds of more or less practically useless observational studies.
I was thus very happy to see that the scientists from the University of Copenhagen did not content themselves with correlating the individual gains of their young and old subjects with the corresponding vitamin D levels. Instead, they designed a randomized controlled trial in which they "investigate[d] whether vitamin-D intake during 12 weeks of resistance training has an additive effect on muscle hypertrophy and strength" (Agergaard. 2015) in Healthy, sedentary young (aged 20–30 years) and elderly (aged 60–75 years) Caucasian men living within the local community in Copenhagen:
"We hypothesized that intake of vitamin-D plus calcium would improve the outcome of three months of resistance training in healthy untrained individuals resulting in greater muscle strength and hypertrophy compared to a training control-group supplemented with calcium alone (placebo). Moreover, we hypothesized that resistance exercise would increase the mRNA expression of VDR and CYP27B1. The study included a group of young and a group of elderly individuals to elucidate a possible blunted hypertrophic response in the aging muscle" (Agergaard. 2015).The study took place at Bispebjerg Hospital, Copenhagen, Denmark (latitude of 56°N). Inclusion was continuous from November 17, 2010 to December 21, 2010 and the last subject completed the study on April 25, 2011. Thus, the study was conducted in a period of low UVB irradiation from sunlight. The risk of interference by uncontrolled sun-exposure was thus low. About as low as I suppose some of you will say the supplementation dose was. The latter consisted of either
- placebo supplementation with 800mg of calcium per day, or
- vitamin D + calcium at a dosage of 48µg (1920 IU) vitamin-D 3 + 800 mg calcium/day
You're too lazy to read and want some extra-information, also on the topic of fat cell cellularity, obesity and body weight regain (yoyo effect?) - Download yesterday's installment of Super Human Radio and listen to my interview an add-free version right here!The scientists probably would have dosed higher, but since the maximum advisable daily dose according to the Danish Health and Medicines Authority is 50 μg, i.e. 2000 IU, they probably felt that their hands were tied.
|Figure 1: Flowchart showing a young and b elderly subjects from first contact to end of study (Agergaard. 2015)|
- During the first 6 training sessions, participants completed 3 sets of 12–15 repetitions at 65–70 % of 1RM.
- During session 7–12, participants performed 3 sets of 10–12 repetitions at 70–75 % of 1RM, increasing to 4 sets at 70–75 % of 1RM during session 13–18.
- From session 19 and onwards, participants performed 5 sets with training load progressing from 8–10 repetitions at 75–80 % of 1RM in session 19–27 to 6–8 repetitions at 80–85 % of 1RM in session 28–36 .
A similar negligence can be observed with regard to the role of the vitamin D receptors on its various target organs. While we know that their expression increases with resistance training (no added increase was observed with vitamin D supplementation in the study at hand in contrast to a recent study by Makanae et al. (2015) in rodents), we still have almost no clue how they interact with free and bound vitamin D; and only recently researchers like Jia et al. (2015) have begun to investigate how certain vitamin D receptor polymorphisms (gene types) like the rs739837 gene are associated with increased risk of T2DM. In conjunction with the role of genetic polymorphisms of the binding proteins, the whole system is at the moment thus way too too complex for us to make predictions on a population or even sub-population levels (like the elderly, men and women at an increased risk of cancer, or patients with autoimmune diseases, or athletes).
|Figure 2: Serum vitamin D levels at all time-points during the study (I added the markups for the zones to the original figure from Agergaard to make it easier for you to interpret the data).|
- No group effects - The first thing you should realize is that there were no significant inter-group differences and thus no group effects in response to the provision of vitamin D3 vs. placebo. This does imply that neither the increased size gains (A) in the vitamin D group in the young nor the decreased gains in the vitamin D group in the old subjects was statistically significant. The same can be said, albeit in the opposite directions for the strength increases (B) and the relative strength increases (C) in the young subjects.
- Significant time effects - Since subjects in both groups still gained significant amounts of muscle and strength, the one thing the study does confirm is the efficacy of resistance training as strength and mass builder in young and old.
- Significant group effect on relative strength in the elderly - Due to the reversal of the observations compared to the young group (lower size gains + higher strength gains in the older, higher size + lower strength gains in the younger subjects), the relative strength of the older subjects has improved by vitamin D supplementation (p = 0.008, not correctly indicated in Figure 3) - a result that stands in line with previous research like Moreira-Pfrimer et al. (2009) where the provision of 150,000 IU once a month during the first 2 months, followed by 90,000 IU once a month for another 4 months enhanced both, the 25(OH)D levels and the lower limb muscle strength of the > or =60 year old subjects, even in the absence of any regular physical exercise practice.
|Figure 5: Correlation between Quadriceps ΔCSA, ΔIsometric strength, Δstrength/CSA and 25(OH)D (Agergaard. 2015)|
- Agergaard, Jakob, et al. "Does vitamin-D intake during resistance training improve the skeletal muscle hypertrophic and strength response in young and elderly men?–a randomized controlled trial." Nutrition & metabolism 12.1 (2015): 32.
- Bischoff-Ferrari, Heike A., et al. "Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes." The American journal of clinical nutrition 84.1 (2006): 18-28.
- Chun, Rene F., et al. "Vitamin D and DBP: the free hormone hypothesis revisited." The Journal of steroid biochemistry and molecular biology 144 (2014): 132-137.
- Garcia, Leah A., et al. "1, 25 (OH) 2 vitamin D 3 enhances myogenic differentiation by modulating the expression of key angiogenic growth factors and angiogenic inhibitors in C 2 C 12 skeletal muscle cells." The Journal of steroid biochemistry and molecular biology 133 (2013): 1-11.
- Garcia, Leah A., et al. "1, 25 (OH) 2vitamin D3 stimulates myogenic differentiation by inhibiting cell proliferation and modulating the expression of promyogenic growth factors and myostatin in C2C12 skeletal muscle cells." Endocrinology 152.8 (2011): 2976-2986.
- Glendenning, Paul, et al. "Calculated free and bioavailable vitamin D metabolite concentrations in vitamin D-deficient hip fracture patients after supplementation with cholecalciferol and ergocalciferol." Bone 56.2 (2013): 271-275.
- Guralnik, Jack M., et al. "Lower-extremity function in persons over the age of 70 years as a predictor of subsequent disability." New England Journal of Medicine 332.9 (1995): 556-562.
- Jia et al. "Vitamin D Receptor Genetic Polymorphism Is Significantly Associated with Risk of Type 2 Diabetes Mellitus in Chinese Han Population." Arch Med Res. (2015): Ahead of print.
- Ko, Min Jung, et al. "Relation of serum 25-hydroxyvitamin D status with skeletal muscle mass by sex and age group among Korean adults." British Journal of Nutrition (2015): 1-7.
- Koplin, Jennifer J., et al. "Polymorphisms affecting vitamin D–binding protein modify the relationship between serum vitamin D (25 [OH] D 3) and food allergy." Journal of Allergy and Clinical Immunology (2015).
- Makanae, Yuhei, et al. "Acute bout of resistance exercise increases vitamin D receptor protein expression in rat skeletal muscle." Experimental physiology 100.10 (2015): 1168-1176.
- Moreira-Pfrimer, Linda DF, et al. "Treatment of vitamin D deficiency increases lower limb muscle strength in institutionalized older people independently of regular physical activity: a randomized double-blind controlled trial." Annals of Nutrition and Metabolism 54.4 (2009): 291-300.